GRAND JUNCTION, Colo. (KKCO) – New details are emerging about the death of a child last night at Powderhorn.

Two-year-old William Jensen died Tuesday night inside a red Toyota 4 Runner that was on Powderhorn Drive off of Highway 65, according to the boy’s step-grandfather Robert Mathena.

William’s four-year-old brother, Tyler, was in the vehicle with him. Tyler was rushed to a local hospital on the CareFlight helicopter, and then he was transferred to Children’s Hospital in Denver where he has been placed on life-support. His condition is unknown.

Mathena believes their mother, Heather, left Tyler and William in the running vehicle, where they were either suffocating or poisoned by carbon monoxide, he says.

Mathena is the step-father of Eric Jensen—the boys’ father—who died in a car accident in Rifle on Oct. 10, 2012.

The Mesa County Sheriff’s Office is waiting on the coroner to release William’s cause of death. After that, investigators will know how best to proceed with the case.

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